This invention relates to a drive control system for display devices for controlling the driving of the display elements arranged for keys or operation switches such as a tone select switch, etc.
Hitherto, for controlling the driving of the display elements provided for respective operation switches mounted in an electronic apparatus, it has been in practice to provide control lines each for each of the display elements and supply drive signals independently of the lines. For example, light-emitting elements (LEDs) are turned on and off as the display elements by changing a control line voltage to a low or high level.
However, where the aforementioned method is applied to an electronic musical instrument, where a number of operation switches such as a tone select switch for selecting the tone and a rhythm select switch for selecting the rhythm are used, a large number of control lines for the display elements provided for the operation switches have to be used. This complicates the wiring, which has been a drawback in view of mass production.
When practicing the performance of a new piece of music using a musical instrument having a keyboard, it is usual to judge the pitch and interval of the musical sound to be produced next, and also the position of a pause from the score, and to operate keys on the keyboard correspondingly. Although this practice is not so difficult to one who has acquired a certain skill of playing the instrument, for the beginner it takes a considerable time to operate keys while watching the score so as to perform a desired piece of music. The fact that practice requires a great deal of time often causes a beginner to give up his intention to master a piece. In this respect, instruments, in which LEDs are provided in correspondence to respective keys in the neighborhood of the keyboard so that at the time when a key is depressed an LED for the key to be operated next is turned on to facilitate the practice of the trainer, thus permitting the trainer to become able to easily perform the piece in a short period of time, have been contemplated. In this case, the control of the LEDs has been done by providing control lines each for each of the LEDs and changing the control line voltage to low or high level for turning on or off the LEDs.
With this method, however, if there are keys for five octaves, i.e., 60 keys, 60 display elements are necessary. In this case, wiring of the electronic musical instrument is extremely complicated, and the efficiency of the wiring operation is low.